The European standard EN ISO 20345 separates safety shoes into different classes of protection. Basic requirements of the standard for optimum protection apply to the upper material (leather, rubber or other synthetic materials) and the toe cap (steel, aluminium or plastic). The anti-slip quality of the soles is also crucial. Work shoes which only meet the basic requirements of the standard EN ISO 20345, are identified with the protection class SB. The individual protection classes expand upon these basic requirements with specific features.